Mount Isa Mines implements emergency concentrate storage following severe flooding

Enabled by the granting of a Temporary Emissions License (TEL), Mount Isa Mines (MIM) has begun operating additional concentrate storage, allowing the company to temporarily increase zinc concentrate capacity at its Star Gully Run of Mine (ROM) pad.

The approval was issued in response to extraordinary flooding events that disrupted transport routes and posed risk to the continued production of zinc, lead and copper across North Queensland.

Unprecedented weather impacts operations

In late December 2025, the North Queensland region experienced severe monsoonal rainfall, leading to widespread flooding, Julia Creek recorded 314mm of rain over 72 hours (29–31 December), a rare event with an estimated annual exceedance probability of a 1 in 200-year flood event.

The extreme weather caused extensive damage to transport infrastructure:

• The rail line connecting MIM to Townsville became partially inoperable.
• Road networks in the region were closed, limiting alternative transport options.
• Localised and inland flooding disrupted contingency measures, including road transport of zinc concentrate.

These conditions led to zinc concentrate stockpiles reaching capacity at existing authorised storage areas, with the risk of significant operational and financial impacts if additional storage was not made available.

The Temporary Emissions License ensures operational continuity

With the approval now in effect, MIM is authorised to store surplus zinc concentrate at the Star Gully ROM pad, which had previously been identified in a 2019 options analysis as the safest and most environmentally appropriate site for temporary storage.

The site offers key advantages:

• Minimised material movement: All surplus concentrate is being stored in a single, controlled location.
• Operational efficiency: Heavy machinery can access the site easily, allowing implementation of environmental and safety controls under Condition C22.
• Environmental risk management: Air quality modelling indicates low risk from storage at the Star Gully ROM pad, ensuring protection of nearby sensitive receptors.

Alternative storage options, such as containerising concentrate or increasing road haulage, were assessed but deemed unsafe or logistically unfeasible due to ongoing flood impacts.

Implementation timeline

Following the approval on 9 January 2026, MIM immediately commenced storing concentrate in the newly authorised area. The license permits storage at Star Gully ROM until regular rail services resume, with activities expected to conclude within three calendar months, subject to extension if further delays occur.

By promptly implementing the approval, MIM is ensuring uninterrupted production, while continuing to uphold strict environmental and safety standards. The temporary storage solution at Star Gully ROM allows the company to manage the impacts of unprecedented weather conditions, reduce disruptions to the supply chain, and maintain its contribution to regional and state productivity.

As of the date of publication, Mount Isa Mines has been granted an extension until 9 July 2026. Since late December 2025, rail operations have been disrupted by multiple flooding and damage-related outages, resulting in a total of 54 days of closure. These disruptions created a significant backlog of concentrate awaiting transport, with approximately 63,420 wmt moved by rail and 2,684 wmt by road to date. Stockpiles at the Star Gully ROM pad are currently estimated at around 25 kt (down from a peak of 32 kt) and are being progressively reduced as shipments to the Port of Townsville resume.